This application claims the benefit of Korean Application No. 2001-76071, filed Dec. 4, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a microwave oven, and more particularly to a microwave oven comprising a plurality of microwave dispersing apparatuses which disperse high-frequency electromagnetic waves and are arranged in a row below a cooking cavity so as to uniformly radiate the high-frequency electromagnetic waves into the cooking cavity.
2. Description of the Related Art
In general, a microwave oven is an electrically operated oven which cooks food disposed in a cooking cavity using high-frequency electromagnetic waves generated from a magnetron installed in a machine room. Specifically, such a microwave oven radiates high-frequency electromagnetic waves into a cooking cavity to repeatedly excite the molecular bonds of moisture laden in food. This excitation generates an intermolecular frictional heat within the food to cook the food.
A cooking cavity of a microwave oven includes an opening which is provided at its front, an air inlet and outlet holes which are provided at its sidewalls, and a cooking tray which receives food to be cooked, and is disposed on a bottom of the cooking cavity. A machine room of the microwave oven includes electrical elements such as a magnetron, a high-voltage transformer, a high-voltage condenser which generates high-frequency electromagnetic waves, and a cooling fan which cools the above electrical elements. The cooking cavity is partitioned from the machine room by one of the sidewalls of the microwave oven.
A microwave oven can be classified into a turntable type microwave oven and a stirrer type microwave oven. A turntable type microwave oven rotates a cooking tray at a low speed to uniformly radiate food with high-frequency electromagnetic waves. A stirrer type microwave oven includes a microwave dispersing apparatus and a waveguide which is provided to one of an upper wall, a lower wall and sidewalls of the microwave oven. The waveguide allows a cooking cavity to communicate with a machine room as the waveguide is provided at a portion extended into the machine room having a magnetron and at a portion disposed in the cooking cavity having the microwave dispersing apparatus. The microwave dispersing apparatus disperses high-frequency electromagnetic waves guided by the waveguide to the cooking cavity so as to uniformly radiate the high-frequency electromagnetic waves to food.
The present invention relates to a stirrer type microwave oven. FIGS. 1 and 2 show a conventional stirrer type microwave oven having a waveguide 10 and microwave dispersing apparatuses 15 that are disposed below a cooking cavity 1. FIG. 2 is a cross-sectional view taken along line IIxe2x80x94II of FIG. 1.
As shown in FIGS. 1 and 2, the conventional stirrer type microwave oven includes a cabinet (not shown) which defines an exterior of the microwave oven and in which the cooking cavity 1 and a machine room 2 are partitioned. The cooking cavity 1 is configured into a box shape having an opening which receives food to be cooked, and a cooking tray 3 which is provided at a bottom of the cooking cavity 1. To rotate the cooking tray 3 at a low speed, the cooking tray 3 is centrally connected at its lower surface to a motor 4. The cooking tray 3 cooperates with the microwave dispersing apparatuses 15 (described later) so as to more uniformly cook the food. Alternatively, the cooking tray 3 may be fixedly mounted on the bottom of the cooking cavity 1 without the motor 4 so as to cook the food placed on the cooking tray 3 with only the high-frequency electromagnetic waves that are uniformly generated from the microwave dispersing apparatuses 15.
The machine room 2 includes a magnetron 5, a high-tension transformer (not shown), a high voltage condenser (not shown) which applies a high voltage current to the magnetron 5, and a cooling fan (not shown) which cools the above electrical elements.
The waveguide 10 is disposed below the cooking cavity 1 and the machine room 2, and guides the high-frequency electromagnetic waves generated from the magnetron 5 to the cooking cavity 1. The waveguide 10 is configured to have an approximately hexahedral box shape having a large surface area, and partially extends to the machine room 2. The magnetron 5 is installed in a portion of the waveguide 10, which is extended to the machine room 2.
The waveguide 10 comprises openings 11 which are formed at approximately a middle portion of the cooking cavity 1 so as to be located at the same distance from the magnetron 5 and are positioned perpendicular to a front face of the cooking cavity 1. High-frequency electromagnetic waves generated from the magnetron 5 are guided by the waveguide 10 and radiated into the cooking cavity 1 through the openings 11.
The waveguide 10 further includes the microwave dispersing apparatuses 15 to disperse the high-frequency electromagnetic waves, which are guided by the waveguide 10 and introduced through the openings 11, into the cooking cavity 1. The microwave dispersing apparatuses 15 are positioned so as to align with the openings 11.
Each of the microwave dispersing apparatuses 15 comprises a motor 16 which is disposed below the waveguide 10, a dispersing fan 17 which is disposed above the opening 11 of the waveguide 10, and a driving shaft 18 connected between the motor 16 and the dispersing fan 17 which transmits a turning force from the motor 16 to the dispersing fan 17.
The high-frequency electromagnetic waves are first generated from the magnetron 5 and then guided by the waveguide 10. The high-frequency electromagnetic waves in the waveguide 10 pass through the openings 11, which are disposed at a middle portion of the cooking cavity 1 and spaced at a certain distance from each other. Subsequently, the high-frequency electromagnetic waves are reflected diffusely by a rotation of the dispersing fans 17 and dispersed into a region of the cooking cavity 1 as the cooking tray 3 is rotated at a low speed. The high-frequency electromagnetic waves are dispersed into an internal space of the cooking cavity 1 so as to evenly cook the food placed on the cooking tray 3.
However, since the above-mentioned conventional stirrer type microwave oven includes openings disposed at an approximately middle portion of a cooking cavity and spaced at the same distance from a magnetron, so as to equally distribute high-frequency electromagnetic waves to both of the openings, a waveguide must inevitability have a surface area occupying nearly a full surface area of the cooking cavity. Hence, the size and manufacturing cost of the conventional stirrer type microwave oven must be increased due to the structural provision of its waveguide. In addition, since the openings are positioned perpendicular to a front face of the cooking cavity, where the cooking cavity has a rectangular shape with a front width larger than a side width parallel to the openings, dispersion of the high-frequency electromagnetic waves toward both sides of the cooking cavity is not sufficiently achieved. Therefore, food in the cooking cavity of the conventional stirrer type microwave oven is unevenly cooked.
Accordingly, it is an object of the present invention is to provide a microwave oven having openings and microwave dispersing apparatuses which are provided at a bottom of a cooking cavity and are in alignment with a magnetron so as to reduce the size of a waveguide and evenly disperse high-frequency electromagnetic waves to all sides of the cooking cavity.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided a microwave oven comprising a main body having a cooking cavity and a machine room which is partitioned from the cooking cavity, a waveguide which is disposed below the cooking cavity and the machine room, a magnetron which is housed in the machine room and coupled to the waveguide, openings which are formed at the waveguide and allow communication between the waveguide and the cooking cavity, and microwave dispersing apparatuses which are disposed at corresponding ones of the openings and disperse high-frequency electromagnetic waves, wherein the openings comprise a first opening which is located at the waveguide and a second opening which is located between the first opening and the magnetron.
According to an aspect of the present invention, the waveguide comprises a laterally elongated structure having a width smaller than the width of the cooking cavity. The center of the first opening is disposed at a first location away from the magnetron by a distance corresponding to one of odd numbers times a half-wavelength of a standing wave in the waveguide. The center of the second opening is disposed at a second location which is offset from another distance away from the magnetron corresponding to another one of the odd numbers times the half-wavelength of the standing wave in the waveguide.
According to another aspect of the present invention, both centers of the first and second openings are disposed at corresponding ones of locations away from the magnetron by distances corresponding to corresponding ones of odd numbers times the half-wavelength of the standing wave in the waveguide, wherein the size of the second opening is smaller than the first opening.
According to yet another aspect of the present invention, both centers of the first and second openings are disposed at corresponding ones of locations away from the magnetron by distances corresponding to corresponding ones of odd numbers times the half-wavelength of the standing wave in the waveguide, wherein the second opening comprises a plurality of slits which extend laterally along the length of the waveguide.
According to still another aspect of the present invention, the microwave oven may include a downward microwave dispersing apparatus which downwardly disperses the high-frequency electromagnetic waves reflected by the microwave dispersing apparatuses installed at the bottom of the cooking cavity, wherein the downward microwave dispersing apparatus is installed at an upper portion of the cooking cavity.